1. Field of the Invention
This invention relates to zoom taking lenses for photographic single lens reflex (SLR) cameras.
2. Description Relative to the Prior Art.
SLR cameras are known which include a camera body which supports photographic film in a film plane, a taking lens for imaging an object onto the film at the film plane, a shutter for controlling the flow of light to the film plane for determining the duration of the photographic exposure, and a viewfinder system for viewing the image which the lens would create on the film plane. The viewfinder system usually includes reflective means, in the form of a mirror, movable between a position in which it intercepts light rays which are directed by the taking lens towards the film plane and directs them laterally of the axis of the taking lens for viewing, and a position in which it is out of the way of the rays from the taking lens and allows those rays to approach the film plane. The first-mentioned position of the mirror may be termed its viewing position and the second-mentioned position may be termed its taking position.
In known camera and zoom lens combinations the mirror is behind the rearmost element of the lens. Such position of the mirror inevitably requires that the lens have a long back-focal-length. Additionally, the zooming motions must take place in front of the mirror. This restriction determines the first order properties of the system and usually results in large element diameters and/or lens length.
It is an object of the present invention to overcome the above restrictions.